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How-To Geek

HDMI allows you to connect almost any device to a TV or another external display, but HDMI requires a wired connection. You might assume there’d be a well-supported standard for wireless displays, but you’d be wrong.

When it comes to mirroring a device’s screen wirelessly or using it as a remote-control for media displayed on another screen, there is still a wide variety of competing standards fighting it out in the market.

AirPlay

AirPlay is Apple’s wireless display standard. It allows you to stream video from an iPhone, iPad, or Mac to an Apple TV. Using AirPlay, you can display the contents of your Mac’s desktop, start a video in an app on your iPhone and “push” it to your TV, or play a game on your iPad and mirror your display on your TV.

Apple’s AirPlay standard is flexible enough to work in two different ways. It can use display mirroring to mirror the contents of a device’s display, or use a streaming mode that’s smarter. For example, you could play a video in an app on an iPhone and use the playback controls on your iPhone to control the video on your TV. Even while fiddling with the playback controls on your iPhone’s screen, they wouldn’t appear on your TV — AirPlay is smart enough to stream only the content you want to see on the display.

AirPlay works very well, but it has a big limitation — it only works with Apple devices. If you have a Mac, iPhone, iPad, and Apple TV, you’ll be happy with it. If you want to stream from a Windows laptop or to a device that isn’t an Apple TV, you’re out of luck.

Miracast

Miracast is an industry-wide standard that’s essentially a response to Apple’s AirPlay. Miracast support is build into Android 4.2+ and Windows 8.1, allowing Android smartphones, Windows tablets and laptops, and other devices to wirelessly stream to Miracast-compliant receivers.

In theory, Miracast is great. In practice, Miracast hasn’t worked out so well. While Miracast is theoretically a standard, there are only a handful of Miracast receivers out there that actually work well in practice. While devices are supposed to interface with other devices that support the standard, many Miracast-certified devices just don’t work (or don’t work well) with Miracast-certified receivers. The standard seems to have collapsed in practice — it’s not really a standard. Check out this table of test results to see just how much of an incompatible mess Miracast seems to be.

Another problem is that the standard doesn’t mandate devices be branded with the “Miracast” brand. Manufacturers have taken to calling their Miracast implementations other things. For example, LG calls their Miracast support “SmartShare,” Samsung calls it “AllShare Cast,” Sony calls it “screen mirroring, ” and Panasonic calls it “display mirroring.” You might pick up a new Samsung TV, see the “AllShare Cast” logo on the box, and not be aware that this is theoretically a Miracast-compatible TV. You’d probably assume that it only worked with other Samsung devices supporting AllShare Cast — and you might not be wrong, considering how many theoretically compatible Miracast devices are incompatible with each other!

You might assume that, since Microsoft added built-in Miracast support to Windows 8.1, their Xbox One console would function as a Miracast receiver. This would make streaming from a Windows 8.1 tablet to your TV via your Xbox One possible and easy. You’d be wrong — the Xbox One can’t function as a Miracast receiver.

In other words, Miracast isn’t doing too well. Even if it were, there’s another problem: Miracast only offers display mirroring. You wouldn’t be able to stream a video from your phone on your TV without the playback controls appearing on your TV while you used them, for example.

WiDi

WiDi is short for Intel Wireless Display, a feature associated with Intel’s Wi-Fi Direct standard. This is Intel’s attempt at offering a wireless video and audio streaming system that could compete with Apple’s AirPlay. WiDi never saw much uptake.

When Google launched the Nexus 4 with Android 4.2 in 2012, they talked up its support of Miracast. Soon, they said, you’d be able to buy cheap Miracast-compatible receivers that you could plug into your TV’s HDMI port. The wireless display problem would be solved, enabling easy display-mirroring from Android and Windows devices.

These cheap, compatible receivers failed to materialize. Instead, a year later, Google launched the Chromecast. A Chromecast is a cheap receiver that plugs into your TV’s HDMI port, but it uses something called the DIAL (DIscover And Launch) protocol. To use the Chromecast, you open an app on your Android phone — Netflix, for example. You tell Netflix to play a video to your Chromecast. The Chromecast then connects to the Internet and plays the video, allowing you to control its playback via the app on your smartphone.

In this way, your smartphone allows you to discover videos, launch them on the Chromecast, and control their playback. The Chromecast doesn’t simply display the contents of your device’s screen. However, Chromecast also offers a feature that lets you stream your entire desktop or the contents of a Chrome tab to your TV via the Chromecast — just like AirPlay.

Like Microsoft’s Xbox One, Google’s Chromecast doesn’t support Miracast at all. The Chromecast is clearly an example of Google throwing their hands up in the air and giving up on Miracast, at least in the short term. Considering all the problems with Miracast and how well Chromecast works, Google appears to have made the right decision.

DLNA isn’t really a wireless display solution. Instead, it’s simply a way to take content on one device and play it on another. For example, you might open Windows Media Player on your PC and use the Play To feature to play a video file from your computer’s hard drive to an audio/video receiver connected to your TV, such as a game console. Compatible devices automatically advertise themselves on the network so they’d appear in the Play To menu without any further configuration needed. The device would then connect to your computer over the network and stream the media you selected.

You can still use DLNA to stream media from a Windows 8.1 PC to an Xbox One. However, the standard was clearly designed years ago — it assumes you have local media. Play To only allows you to play local media files like pictures, videos, and music on your hard drive. There’s no way to play videos from Netflix or YouTube, stream music from an online service, display a presentation and control it on your screen, or just display the contents of your desktop.

AirPlay arrived in 2010 and other companies are still struggling to match it. If you’re one of the many people who would like to see an open standard that allows non-Apple devices to wirelessly share their displays, the Miracast mess has been tough to watch.

I want to point out that Miracast actually does support "smart" streaming a la Airplay. However, this is built into the casting device and not the receiver. For example, Samsung devices will push only the video and not the ui elements when playing back a video using hardware rendering - exactly how Airplay does it. You can change functions and seek and generally interact with the phone while the video is playing on the TV without affecting that picture. Furthermore, the video is only played on the TV while the phone displays only the ui elements and a black screen where the video would usually be. This works in any app that plays the video using the hardware decoders - the stock video player, mx player, even YouTube all function like this. Software rendered videos and games display everything including the ui as the article says.

Problem is, not every device/rom support this functionality. Samsung roms/devices support it, but most custom roms don't. This includes paranoid android, cyanogenmod, aokp, etc. These display exactly what you see on your device on the TV - just straight up dumb mirroring. I'm not sure what other manufacturers support this functionality since I only have Samsung devices.